1 00:00:00,010 --> 00:00:03,040 Bell Tone 2 00:00:03,060 --> 00:00:07,090 Hi, this is Alex Young. I'm a heliophysicist 3 00:00:07,110 --> 00:00:11,140 at NASA's Goddard Space Flight Center. And many of you may have seen the 4 00:00:11,160 --> 00:00:15,190 video recently that showed the sun for the past three years 5 00:00:15,210 --> 00:00:19,240 observed by the Solar Dynamics Observatory. I also saw this recently, 6 00:00:19,260 --> 00:00:23,340 thought it was a really cool video and I want to share with you some of the interesting 7 00:00:23,360 --> 00:00:27,400 features I noticed in the video. -MUSIC- 8 00:00:27,420 --> 00:00:31,460 If you see that big black disk that moves over the sun, that's 9 00:00:31,480 --> 00:00:35,540 the moon--what we call a lunar transit. That's when the moon is moving 10 00:00:35,560 --> 00:00:39,600 between the sun and the SDO spacecraft. 11 00:00:39,620 --> 00:00:43,660 It almost looks like a perfect circle, but if you look really 12 00:00:43,680 --> 00:00:47,740 really close on the edge, you see these little tiny humps. Those 13 00:00:47,760 --> 00:00:51,820 are the mountains on the moon. Just an amazing thing you can see with 14 00:00:51,840 --> 00:00:55,940 these incredibly high-resolution cameras. We're looking 15 00:00:55,960 --> 00:01:00,020 at the 171 angstrom wavelength. This is extreme 16 00:01:00,040 --> 00:01:04,160 ultraviolet. And it's showing us the solar atmosphere at about 17 00:01:04,180 --> 00:01:08,180 a million degrees Fahrenheit. And if you look at this image, you can 18 00:01:08,200 --> 00:01:12,210 see all of these bright patches, these are active 19 00:01:12,230 --> 00:01:16,240 regions associated with sunspots. And then you even see 20 00:01:16,260 --> 00:01:20,270 loops. These are huge structures many times the size of 21 00:01:20,290 --> 00:01:24,300 Earth that are magnetic fields holding in 22 00:01:24,320 --> 00:01:28,310 this hot solar plasma. One of the 23 00:01:28,330 --> 00:01:32,340 things that's amazing about this is there's so much stuff going on in this 24 00:01:32,360 --> 00:01:36,360 image as we're looking over time. There's a really big 25 00:01:36,380 --> 00:01:40,390 flash on one side of the sun--that's a solar flare. And in this 26 00:01:40,410 --> 00:01:44,430 case it's the largest solar flare that happened during this particular 27 00:01:44,450 --> 00:01:48,470 solar activity cycle. One of the coolest things that we 28 00:01:48,490 --> 00:01:52,500 can see from this video is the simple fact that the sun 29 00:01:52,520 --> 00:01:56,540 rotates around its axis. The center near the equator 30 00:01:56,560 --> 00:02:00,570 takes about 25 days for it to rotate all the way 31 00:02:00,590 --> 00:02:04,600 around and come back to the same place. Now, I'm pointing this out because 32 00:02:04,620 --> 00:02:08,630 the sun has a special feature, something called differential rotation. 33 00:02:08,650 --> 00:02:12,650 A point on the equator actually moves faster 34 00:02:12,670 --> 00:02:16,670 than a point closer to the north or south pole. 35 00:02:16,690 --> 00:02:20,700 One thing that happens is sometimes the images move, the sun 36 00:02:20,720 --> 00:02:24,740 moves around or even rolls. But that's actually the 37 00:02:24,760 --> 00:02:28,770 spacecraft moving, not the sun. SDO has to 38 00:02:28,790 --> 00:02:32,810 occasionally roll the entire spacecraft in order to 39 00:02:32,830 --> 00:02:36,850 calibrate the cameras and instrumentation on board. 40 00:02:36,870 --> 00:02:40,880 If you notice, those bright patches, those active 41 00:02:40,900 --> 00:02:44,930 regions, start off towards the poles 42 00:02:44,950 --> 00:02:48,950 of the sun and as we move in time, they start to 43 00:02:48,970 --> 00:02:52,990 slowly creep towards the equator. This is part of what we call 44 00:02:53,010 --> 00:02:57,040 the solar activity cycle or solar cycle. As we 45 00:02:57,060 --> 00:03:01,080 move from very low activity, with very few sunspots, 46 00:03:01,100 --> 00:03:05,150 to high activity, with a lot of sunspots. 47 00:03:05,170 --> 00:03:09,190 This is something that happens again and again, and it's happened 48 00:03:09,210 --> 00:03:13,230 for millions of years. -MUSIC- 49 00:03:13,250 --> 00:03:17,310 -MUSIC- 50 00:03:17,330 --> 00:03:21,370 And now we can see the sun 51 00:03:21,390 --> 00:03:25,420 in multiple wavelengths of light simultaneously. We see 52 00:03:25,440 --> 00:03:29,470 the visible sun, where you can see the dark sunspots. 53 00:03:29,490 --> 00:03:33,540 And then if you look at the 171 extreme ultraviolet 54 00:03:33,560 --> 00:03:37,600 you see the corresponding bright areas and the magnetic 55 00:03:37,620 --> 00:03:41,710 loops coming from them. If we go to the 193 56 00:03:41,730 --> 00:03:45,790 you see even more structure and you see these dark patches. 57 00:03:45,810 --> 00:03:49,850 And this is where magnetic fields are open out into space 58 00:03:49,870 --> 00:03:53,920 letting out something called the solar wind in these very 59 00:03:53,940 --> 00:03:58,040 fast streams of particles. And then the last one, the red 60 00:03:58,060 --> 00:04:02,130 one, is 304 angstrom, and this is showing us what we 61 00:04:02,150 --> 00:04:06,230 call the chromosphere. And these red areas are often visible 62 00:04:06,250 --> 00:04:10,330 when you see the sun from total solar eclipse. 63 00:04:10,350 --> 00:04:14,480 -MUSIC- 64 00:04:14,500 --> 00:04:18,500 -MUSIC- 65 00:04:18,520 --> 00:04:22,530 Did you see that little tiny black 66 00:04:22,550 --> 00:04:26,560 dot that's close to the north pole on the sun? That's Venus. 67 00:04:26,580 --> 00:04:30,590 Every hundred years or so, it moves in front of the sun 68 00:04:30,610 --> 00:04:34,630 giving us this rare and amazing astronomical 69 00:04:34,650 --> 00:04:38,660 event. -MUSIC- 70 00:04:38,680 --> 00:04:42,670 -MUSIC- 71 00:04:42,690 --> 00:04:46,700 -MUSIC- 72 00:04:46,720 --> 00:04:50,730 -MUSIC- 73 00:04:50,750 --> 00:04:54,760 Beeping 74 00:04:54,780 --> 00:05:03,784 Beeping